Disorder-induced double resonant Raman process in graphene

An analytical study is presented of the double resonant Raman scattering process in graphene, responsible for the D and D$^{\prime}$ features in the Raman spectra. This work yields analytical expressions for the D and D$^{\prime}$ integrated Raman intensities that explicitly show the dependencies on laser energy, defect concentration, and electronic lifetime. Good agreement is obtained between the analytical results and experimental measurements on samples with increasing defect concentrations and at various laser excitation energies. The use of Raman spectroscopy to identify the nature of defects is discussed. Comparison between the models for the edge-induced and the disorder-induced D band intensity suggests that edges or grain boundaries can be distinguished from disorder by the different dependence of their Raman intensity on laser excitation energy. Similarly, the type of disorder can potentially be identified not only by the intensity ratio $I_{\mathrm{D}}/I_{\mathrm{D}^{\prime}}$, but also by its laser energy dependence. Also discussed is a quantitative analysis of quantum interference effects of the graphene wavefunctions, which determine the most important phonon wavevectors and scattering processes responsible for the D and D$^{\prime}$ bands.Comment: 10 pages, 4 figure

The two-echelon capacitated vehicle routing problem: models and math-based heuristics

Multiechelon distribution systems are quite common in supply-chain and logistics. They are used by public administrations in their transportation and traffic planning strategies, as well as by companies, to model own distribution systems. In the literature, most of the studies address issues relating to the movement of flows throughout the system from their origins to their final destinations. Another recent trend is to focus on the management of the vehicle fleets required to provide transportation among different echelons. The aim of this paper is twofold. First, it introduces the family of two-echelon vehicle routing problems (VRPs), a term that broadly covers such settings, where the delivery from one or more depots to customers is managed by routing and consolidating freight through intermediate depots. Second, it considers in detail the basic version of two-echelon VRPs, the two-echelon capacitated VRP, which is an extension of the classical VRP in which the delivery is compulsorily delivered through intermediate depots, named satellites. A mathematical model for two-echelon capacitated VRP, some valid inequalities, and two math-heuristics based on the model are presented. Computational results of up to 50 customers and four satellites show the effectiveness of the methods developed

3D behaviour of a 4 parameter isotropic nonlinear hardening plasticity model for concrete

In general, concrete is a highly nonlinear material with great dependence on the confining stresses, a type of behaviour also common in other granular and quasi-brittle materials. The CEB-FIP Model Code [1] recommends the use of a four-parameter failure criterion to estimate the strength of concrete under multiaxial states of stress. This failure criterion is also known as the Ottosen failure criterion, and it captures with high accuracy the behaviour of these materials, as demonstrated by several researchers, performing experimental test programs. The concrete strength estimation takes into account, with great precision, the effect of the increase in the confining stresses. In order to simulate the monotonic quasi-static multiaxial behaviour of concrete, one possible strategy is to introduce in this failure criterion a hardening parameter and the corresponding evolution law, under the isotropic behaviour framework. In the present work, the concrete compressive strength in the Ottosen failure criterion is assumed as the hardening parameter, and the CEB-FIP Model Code 90 law for the uniaxial nonlinear behaviour of concrete is used to derive the hardening law. In this case, the loading surface is not explicitly defined as a function of the hardening parameter, as in the other more common and simpler isotropic models. As a consequence, some difficulties may emerge, mainly of a numerical nature. In this context, the formulation of the model in a thermodynamically consistent framework is presented. The general behaviour of this model is accessed by the simulation of the monotonic multiaxial loading of concrete elements, and its numerical efficiency is discussed

Conference report : FRPRCS11-11th International Symposium on Fiber Reinforced Polymer for Reinforced Concrete Structures

The 11th International Symposium on Fiber Reinforced Polymer for Reinforced Concrete Structures (FRPRCS11), an event co-sponsored by IIFC, was held 26-28 June at the Vila Flor Cultural Centre of Guimarães City, in Portugal. Following peer review, 148 extended abstracts and full papers were accepted and published in the proceedings. Approximately 170 delegates representing 38 countries and 137 institutions were in attendance. The distribution of papers by theme is indicated in Table 1, where the tendency for a significant research effort on the “Reinforcement and strengthening performance of FRP systems” is clear, forming about one third of the accepted publications. The FRPRCS11 was composed of 20 sessions of 20 minutes presentations including about 5 minutes for discussion of each. The high technical/scientific level of the publications, and especially the enthusiastic and fruitful discussions which occurred during the presentations were highly remarked upon by the conference participants. Prof. Brahim Benmokrane and Prof. Stijn Matthys provided two stimulating keynote lecturers which provided extraordinary contribution to the motivation and enthusiasm of the delegates, and the scientific quality of FRPRCS11. The closing ceremony ended with the announcement of the chairman of the next FRPRCS conference, Prof. Zhishen Wu, who in 2015 will host FRPRCS12 in Nanjing, China

Oviposição, desenvolvimento e reprodução de Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) em diferentes hospedeiros de importância econômica.

The host selection for oviposition by Spodoptera frugiperda (J.E. Smith) among corn, millet, cotton and soybean, and its relationship with the biological characteristics were investigated. Free and non-choice tests for oviposition using plots containing fi ve plants each, from each host in plastic greenhouse, resulted in similar oviposition preference among the host plants. In addition, selected biological characteristics of S. frugiperda were determined in the laboratory with larvae feeding on host leaves, and the combination of leaf and cotton boll. Neonate larvae exhibited low success of colonization on cotton boll compared to the leaves of all other hosts. Spodoptera frugiperda fed only on cotton bolls exhibited longer larval and pupal development, and longer adult life span; however with similar egg production. Larvae fed cotton leaves during six days and then transferred to cotton bolls, however, exhibited development and reproduction similar to those reared on corn or only on cotton leaves. Therefore, the variations on immature stages of S. frugiperda were not related with host selection for oviposition which was similar among the studied hosts. Based on our data, the millet as a winter, rotational, and cover crop is a potential host for S. frugiperda, while leaves and cotton bolls were diets of intermediate suitability as compared to corn and soybean leaves

Group Theory analysis of phonons in two-dimensional Transition Metal Dichalcogenides

Transition metal dichalcogenides (TMDCs) have emerged as a new two dimensional materials field since the monolayer and few-layer limits show different properties when compared to each other and to their respective bulk materials. For example, in some cases when the bulk material is exfoliated down to a monolayer, an indirect-to-direct band gap in the visible range is observed. The number of layers $N$ ($N$ even or odd) drives changes in space group symmetry that are reflected in the optical properties. The understanding of the space group symmetry as a function of the number of layers is therefore important for the correct interpretation of the experimental data. Here we present a thorough group theory study of the symmetry aspects relevant to optical and spectroscopic analysis, for the most common polytypes of TMDCs, i.e. $2Ha$, $2Hc$ and $1T$, as a function of the number of layers. Real space symmetries, the group of the wave vectors, the relevance of inversion symmetry, irreducible representations of the vibrational modes, optical selection rules and Raman tensors are discussed.Comment: 32 pages, 4 figure

Aspectos agronômicos e de qualidade do pequi.

Caracterização botânica; características agronômicas; características químicas do fruto; utilização; considerações finais.bitstream/CNPAT-2010/10884/1/Dc-113.pd